Sphingomyelin synthase 2 affects CD14‑associated induction of NF‑κB by lipopolysaccharides in acute lung injury in mice

Association between Changes in Plasma Metabolism and Clinical Outcomes of Sepsis

Current prognostic biomarkers for sepsis have limited sensitivity and specificity. This study aimed to investigate dynamic lipid metabolomics and their association with septic immune response and clinical outcomes of sepsis. This prospective cohort study included patients with sepsis who met the Sepsis 3.0 criteria. On hospitalization days 1 (D1) and 7 (D7), plasma samples were collected, and patients underwent liquid chromatography with tandem mass spectrometry. A total of 40 patients were enrolled in the study, 24 (60%) of whom were men. The median age of the enrolled patients was 81 (68-84) years. Thirty-one (77.5%) patients had a primary infection site of the lung. Participants were allocated to the survivor (25 cases) and nonsurvivor (15 cases) groups based on their 28-day survival status. Ultimately, a total of 113 lipids were detected in plasma samples on D 1 and D 7, of which 42 lipids were most abundant in plasma samples. The nonsurvival group had significantly lower lipid expression levels in lysophosphatidylcholine (LysoPC) (16 : 0, 17 : 0,18 : 0) and 18 : 1 SM than those in the survival group (p <  0.05) on D7-D1. The correlation analysis showed that D7-D1 16 : 0 LysoPC (r = 0.367, p = 0.036),17 : 0 LysoPC (r = 0.389, p = 0.025) and 18 : 0 LysoPC(r = 0.472, p = 0.006) levels were positively correlated with the percentage of CD3⁺ T cell in the D7-D1. Plasma LysoPC and SM changes may serve as prognostic biomarkers for sepsis, and lipid metabolism may play a role in septic immune disturbances.

Inhibition of sphingomyelin synthase 2 relieves hypoxia-induced cardiomyocyte injury by reinforcing Nrf2/ARE activation via modulation of GSK-3β

Sphingomyelin synthase 2 (SMS2) is a vital contributor to tissue injury and affects various pathological processes. However, whether SMS2 participates in the modulation of cardiac injury in myocardial infarction has not been determined. This study aimed to evaluate the potential role of SMS2 in the regulation of cardiomyocyte injury induced by hypoxia, an in vitro model for studying myocardial infarction. Our data revealed that SMS2 expression was significantly upregulated in cardiomyocytes in response to hypoxia. Loss-of-function experiments revealed that knockdown of SMS2 markedly restored the viability of cardiomyocytes impaired by hypoxia, and attenuated hypoxia-evoked apoptosis and reactive oxygen species (ROS) generation. In contrast, cardiomyocytes that highly expressed SMS2 were more sensitive to hypoxia-induced injury. Moreover, SMS2 deficiency enhanced the activation of nuclear factor erythroid 2-related factor 2 (Nrf2) signaling through inactivation of glycogen synthase kinase-3β. Notably, suppression of Nrf2 markedly abrogated SMS2 knockdown-mediated cardioprotective effects on hypoxia-exposed cardiomyocytes. Our results illustrate that downregulation of SMS2 exerts a cardioprotective function by protecting cardiomyocytes from hypoxia-induced apoptosis and oxidative stress through enhancement of Nrf2 activation. Our study indicates a potential role of SMS2 in the modulation of cardiac injury, which may contribute to the progression of myocardial infarction.

Sphingomyelin synthase 1 regulates the epithelial‑to‑mesenchymal transition mediated by the TGF‑β/Smad pathway in MDA‑MB‑231 cells

Breast cancer is the most common cancer in women and a leading cause of cancer‑associated mortalities in the world. Epithelial‑to‑mesenchymal transition (EMT) serves an important role in the process of metastasis and invasive ability in cancer cells, and transforming growth factor β1 (TGF‑β1) have been investigated for promoting EMT. However, in the present study, the role of the sphingomyelin synthase 1 (SMS1) in TGF‑β1‑induced EMT development was investigated. Firstly, bioinformatics analysis demonstrated that the overexpression of SMS1 negatively regulated the TGFβ receptor I (TβRI) level of expression. Subsequently, the expression of SMS1 was decreased, whereas, SMS2 had no significant difference when MDA‑MB‑231 cells were treated by TGF‑β1 for 72 h. Furthermore, the present study constructed an overexpression cells model of SMS1 and these cells were treated by TGF‑β1. These results demonstrated that overexpression of SMS1 inhibited TGF‑β1‑induced EMT and the migration and invasion of MDA‑MB‑231 cells, increasing the expression of E‑cadherin while decreasing the expression of vimentin. Furthermore, the present study further confirmed that SMS1 overexpression could decrease TβRI expression levels and blocked smad family member 2 phosphorylation. Overall, the present results suggested that SMS1 could inhibit EMT and the migration and invasion of MDA‑MB‑231 cells via TGF‑β/Smad signaling pathway.

Synergistic effect of receptor-interacting protein 140 and simvastatin on the inhibition of proliferation and survival of hepatocellular carcinoma cells

Hepatocellular carcinoma is the sixth most prevalent malignant tumor and the third most common cause of cancer-associated mortality. Statins have been investigated for carcinoma prevention and treatment. In addition, receptor-interacting protein 140 (RIP140) has been observed to inhibit the Wnt/β-catenin signaling pathway and cell growth. The present study aimed to investigate whether simvastatin (SV) is able to induce SMCC-7721 cell apoptosis through the Wnt/β-catenin signaling pathway. Initially, a cell model of RIP140 overexpression was established, and then cells were treated with SV. The cell growth, viability and apoptosis were measured by cell counting kit-8 and flow cytometry. Furthermore, the expression levels of RIP140, β-catenin, c-myc and cyclin D1 were detected by reverse transcription-quantitative polymerase chain, western blot analysis and immunofluorescence. The results demonstrated that SV significantly increased the expression of RIP140 in SMCC-7721 cells; however, β-catenin, c-myc and cyclin D1 levels were significantly decreased. Furthermore, the immunofluorescence assay of β-catenin confirmed that SV decreased the content of this protein in SMCC-7721 cells. Notably, RIP140 exerted a synergistic effect on the apoptosis rate induced by SV (RIP140 + SV group), while the alteration in RIP140, β-catenin, c-myc and cyclin D1 levels was more evident in the combination group as compared with the RIP140 or SV alone groups. In conclusion, these results suggested that SV is able to induce the apoptosis of SMCC-7721 cells through the Wnt/β-catenin signaling pathway, as well as that RIP140 and SV exert a synergistic effect on the inhibition of cell proliferation and survival.

Effects of sepsis on the metabolism of sphingomyelin and cholesterol in mice with liver dysfunction

Sepsis is characterized by a severe inflammatory response to infection. With the spread of sepsis, various tissues, including the lungs, liver and kidney, may be damaged. This may finally develop into multiple organ dysfunction syndrome. Sphingomyelin and cholesterol are two main lipids involved in sepsis. The metabolism of sphingomyelin and cholesterol in the livers of mice with sepsis needs to be clarified. To achieve this, the present study intraperitoneally injected mice with PBS, lipopolysaccharide (LPS; 10 mg/kg) and LPS + pyrrolidine dithiocarbamate (PDTC; 30 mg/kg). Subsequently, sphingomyelin and cholesterol content were measured using kits, the sphingomyelin synthase (SMS) activity was measured using thin layer chromatography, and the expression levels of SMS1 and 2, hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR), ATP binding cassette subfamily A member 1 (ABCA1), scavenger receptor class B member 1 (SR-B1) and apolipoprotein A1 (Apo A1) were determined by western blotting in the livers of mice. Results demonstrated that, in the LPS group, sphingomyelin and cholesterol content was significantly increased (P<0.001; n=6), the SMS activity significantly enhanced (P<0.001; n=6), the expression levels of SMS2, HMGCR, ABCA1 and SR-B1 were augmented (P<0.05; n=6), and the expression of Apo A1 was decreased (P<0.05; n=6), whereas SMS1 level only slightly increased with no statistical significance (P>0.05; n=6), compared to the levels in the control group. However, PDTC was able to attenuate these alterations. These results indicated that sphingomyelin and cholesterol content may increase in the liver dysfunction of sepsis by increasing the expression of SMS2, HMGCR, SR-B1 and ABCA1, and downregulating Apo A1.